WorksheetFunction.Gamma_Dist(Double, Double, Double, Boolean) Method

Definition

Namespace:

Microsoft.Office.Interop.Excel

Assembly:

Microsoft.Office.Interop.Excel.dll

Returns the gamma distribution. You can use this function to study variables that may have a skewed distribution. The gamma distribution is commonly used in queuing analysis.

public:
 double Gamma_Dist(double Arg1, double Arg2, double Arg3, bool Arg4);

public double Gamma_Dist (double Arg1, double Arg2, double Arg3, bool Arg4);

Public Function Gamma_Dist (Arg1 As Double, Arg2 As Double, Arg3 As Double, Arg4 As Boolean) As Double

Parameters

Arg1

Double

X - the value at which you want to evaluate the distribution.

Arg2

Double

Alpha - a parameter to the distribution.

Arg3

Double

Beta - a parameter to the distribution. If beta = 1, Gamma_Dist returns the standard gamma distribution.

Arg4

Boolean

Cumulative - a logical value that determines the form of the function. If cumulative is true, Gamma_Dist returns the cumulative distribution function; if false, it returns the probability density function.

Returns

Double

Remarks

If x, alpha, or beta is nonnumeric, Gamma_Dist returns the #VALUE! error value.

If x < 0, Gamma_Dist returns the #NUM! error value.

If alpha ≤ 0 or if beta ≤ 0, Gamma_Dist returns the #NUM! error value.

The equation for the gamma probability density function is:

Figure 1: Gamma probability density function

The standard gamma probability density function is:

Figure 2: Standard gamma probability density function

When alpha = 1, Gamma_Dist returns the exponential distribution with:

Figure 3: Equation

For a positive integer n, when alpha = n/2, beta = 2, and cumulative = true, Gamma_Dist returns (1 - CHIDIST(x)) with n degrees of freedom.

When alpha is a positive integer, Gamma_Dist is also known as the Erlang distribution.